This site explains the differences between the similar (and often confused) Liriope muscari (Border Grass), Liriope spicata (Lilyturf) and Ophiopogon (Mondo Grass). The common name Monkey Grass is used to refer to both Liriope muscari and Ophiopogon.

Liriope muscari (Border Grass, Monkey Grass)

Liriope muscari is a species of low-growing flowering plants from Asia, primarily grown for their tidy low-maintenance grass-like foliage. Liriope muscari is perfect for banks, beds and at the base of trees where roots will not permit grass to grow - an almost indestructible plant for stubborn areas. Outstanding for erosion control. Liriope gracefully fills those spots where nothing else will grow and will choke out most weeds.

Liriope muscari (except for the variety "Big Blue") stays in clump form (does not creep like Liriope spicata), forming mounds 12-24" tall (depending on variety) with white, pink, lavender or purple flower spikes protruding higher. Evergreen in southern zones, several variegated varieties are available. Hardy in shade and part shade, some varieties are hardy in full sun.

Liriope spicata (Lilyturf)

Liriope spicata is a species of low-growing flowering plants from Asia, primarily grown for their tidy low-maintenance grass-like foliage. Liriope spicata is perfect for banks, beds and at the base of trees where roots will not permit grass to grow - an almost indestructible plant for stubborn areas. Outstanding for erosion control. Liriope gracefully fills those spots where nothing else will grow and will choke out most weeds.

Unlike Liriope muscari, Liriope spicata creeps indefinitely and will cover large areas with a uniform bed of dense, arching foliage 10-15" tall. White to lavender flower spikes rise on 10" stalks in late summer. Evergreen in southern zones, a variegated variety is available. Hardy in full shade through full sun.

Ophiopogon (Mondo Grass, Monkey Grass)

Ophiopogon japonicus is a species of evergreen low-growing plants from Japan, primarily grown for their tidy low-maintenance grass-like foliage. Ophiopogon is an excellent ground cover for shady areas, and the dense mat of roots holds the ground well where runoff is a problem. It is widely used as a border around beds, and is good for edging walkways and defining beds.

The dwarf variety is excellent as a groundcover around shady pools or garden statues: its height will not compete with the feature, dark green will contrast better than a bright green grass, and it will require no mowing. Good for erosion control, it is tolerant of salt and drought, and deer tend to avoid it.

The mounding foliage of Ophiopogon is similar to Liriope muscari, but it is shorter (the regular variety is 6-10" tall, the dwarf variety is 2-3" tall). Dwarf mondo grass looks like a perfectly manicured lawn, and is often used as a turf substitute. Hardy in full shade through full sun.

Ornamental grasses come in a variety of tones and textures and most of them persist year round no matter what the weather. These plants are a wonderful addition to any backyard and are ideal for filling in spaces where nothing else seems to grow. They are extremely important for controlling soil erosion and to help reduce soil evaporation. They also provide a lush canvas that allow your brightly colored plants and flowers to truly shine.